1. Field of the Invention
The present invention relates to a method for paging in a wireless access system.
2. Discussion of the Related Art
The following is a brief description of a channel estimation method and pilot signals.
Hereinafter, a paging group and an idle mode of a mobile station, which are related to the embodiments of the present invention, will be described in brief.
FIG. 1 is a diagram illustrating an example of a paging group comprised of a plurality of base stations.
Paging means a function that can identify a location (for example, any base station or any exchange station) of a corresponding mobile station (MS) when an incoming call occurs in mobile communication. As illustrated in FIG. 1, a plurality of base stations (BS) which support an idle mode belong to a paging group to constitute a paging region.
The paging group represents a logical group. The paging group is to provide a neighboring range region that can be paged to a downlink (DL) if there is any traffic targeting a mobile station (MS). And, the paging group should meet the condition to be large enough for a specific terminal to exist for most of time within a same paging group and the condition to be small enough for a paging load to maintain a proper level.
FIG. 1 illustrates four paging groups defined in multiple base stations located in hexagonal lattices. One base station can be included in one or more paging groups. The paging group is defined by a management system. A paging group-action backbone network message can be used in the paging group. Also, a paging controller cam manage a list of mobile stations which are in an idle mode, using a paging-announce message which is one of the backbone network message, and can manage initial paging of all base stations belonging to the paging group.
The idle mode means a support operation that allows a mobile station to periodically receive downlink broadcast traffic transmission even though the mobile station is not subscribed to a specific base station when moving a wireless link condition of multiple base stations.
The mobile station can be benefited by the idle mode as action requirements related to handover and general operation requirements are removed. The idle mode can save the power and management resources used by the mobile station by limiting action of the mobile station to be scanned during a discrete period.
Furthermore, the idle mode provides a simple and proper mode that can notify the mobile station of downlink traffic which is pending. The idle mode can provide benefit to a network and a base station by removing a wireless interface and network handover (HO) traffic from the mobile station which is not active.
Paging is performed in a unit of paging group in the idle mode. Referring to FIG. 1, the mobile station can belong to one or more paging groups, and a paging controller of each paging group performs paging to page the mobile station if a call or a user packet from external network appears. At this time, the paging controller transfers a paging message to all base stations within the paging groups, and the base stations which have received the paging message perform paging by broadcasting MOB_PAG-ADV message to the mobile station.